Abstract
BackgroundA previous meta-analysis found that high dose zinc acetate lozenges reduced the duration of common colds by 42%, whereas low zinc doses had no effect. Lozenges are dissolved in the pharyngeal region, thus there might be some difference in the effect of zinc lozenges on the duration of respiratory symptoms in the pharyngeal region compared with the nasal region. The objective of this study was to determine whether zinc acetate lozenges have different effects on the duration of common cold symptoms originating from different anatomical regions.MethodsWe analyzed three randomized trials on zinc acetate lozenges for the common cold administering zinc in doses of 80–92 mg/day. All three trials reported the effect of zinc on seven respiratory symptoms, and three systemic symptoms. We pooled the effects of zinc lozenges for each symptom and calculated point estimates and 95% confidence intervals (95% CI).ResultsZinc acetate lozenges shortened the duration of nasal discharge by 34% (95% CI: 17% to 51%), nasal congestion by 37% (15% to 58%), sneezing by 22% (−1% to 45%), scratchy throat by 33% (8% to 59%), sore throat by 18% (−10% to 46%), hoarseness by 43% (3% to 83%), and cough by 46% (28% to 64%). Zinc lozenges shortened the duration of muscle ache by 54% (18% to 89%), but there was no difference in the duration of headache and fever.ConclusionsThe effect of zinc acetate lozenges on cold symptoms may be associated with the local availability of zinc from the lozenges, with the levels being highest in the pharyngeal region. However our findings indicate that the effects of zinc ions are not limited to the pharyngeal region. There is no indication that the effect of zinc lozenges on nasal symptoms is less than the effect on the symptoms of the pharyngeal region, which is more exposed to released zinc ions.Given that the adverse effects of zinc in the three trials were minor, zinc acetate lozenges releasing zinc ions at doses of about 80 mg/day may be a useful treatment for the common cold, started within 24 hours, for a time period of less than two weeks.Electronic supplementary materialThe online version of this article (doi:10.1186/s12875-015-0237-6) contains supplementary material, which is available to authorized users.
Highlights
A previous meta-analysis found that high dose zinc acetate lozenges reduced the duration of common colds by 42%, whereas low zinc doses had no effect
If the zinc ion concentration of the mucosa determines the effect of zinc lozenges on the specific symptoms on the particular anatomical region, there might be substantial differences between the effects of zinc on throat symptoms compared with nasal symptoms. The purpose of this meta-analysis is to investigate whether zinc acetate lozenges have different effects on the duration of common cold symptoms originating from different anatomical regions
There was no substantial heterogeneity between the three trials in the effect of zinc acetate lozenges on total common cold duration (P = 0.2; I2 = 41%), and a pooled estimate of a 42% reduction in the total duration of the colds was obtained (Figure 1)
Summary
A previous meta-analysis found that high dose zinc acetate lozenges reduced the duration of common colds by 42%, whereas low zinc doses had no effect. The objective of this study was to determine whether zinc acetate lozenges have different effects on the duration of common cold symptoms originating from different anatomical regions. The benefit appeared to be derived from dissolving the tablet in the mouth, which implied that zinc may have local effects in the pharyngeal region. This observation led the father of the child to conduct a randomized trial, which found that zinc lozenges significantly shortened colds [1]. Acetate does not chemically bind to zinc ions and zinc acetate may be an ideal zinc salt for composing lozenges that release high levels of free zinc ions [6,9,10]
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